Until yesterday I only occassionally read about it, but yesterday I experienced my Ubuntu workstation self-healing from freeze.
I did not take care about how many applications were running and as doing a lot of things in parallel that all take quite a while (downloads in background, file copy operations and installations within virtual machines) I completely forgot about how many virtual machines were started. I was about to start another one when everything started to get really slow. I have 4 GB memory and a small swap partition (because during normal work I hardly get the memory of my Ubuntu full).
The memory at this time really got filled up completely and everything got veeery slow. I wasn't either able to switch windows. I was able to switch to the text console which also was very slow.
I wanted to login and kill a few tasks when I got messages broadcasted to my text console saying that the memory was exhausted. Shortly afterwards I got messages that the system identified Firefox and Thunderbird doing nothing and they were closed (maybe because just consuming memory at this moment). And finally it told that the last VirtualBox machine was consuming a lot of system resources and - was killed.
Flup, flup, everything was fine again. - And hadn't either time to do it manually. And it was doing exactly what I would have done manually - killing the last started virtual machine and closing the applications that were doing nothing (downloads were already finished).
That is simply awesome!